Friction plate wear rate

Post your post 1970 technical queries here

Moderator: Moderators

Electrajohnt
Forum User
Posts: 30
Joined: Mon Jan 18, 2021 7:18 pm
Country of Residence: Mow Cop, England

Friction plate wear rate

Postby Electrajohnt » Sun Feb 21, 2021 1:15 am

I know it’s like how long is a piece of string, but how many miles to wear out a friction plate on R60/6
JohnT

User avatar
Jaythro
Site Admin/Club Member
Posts: 3309
Joined: Sat Nov 12, 2005 1:00 am
Country of Residence: Norn Iron
Location: Islandmagee, County Antrim, North East Ireland

Re: Friction plate wear rate

Postby Jaythro » Sun Feb 21, 2021 10:14 am

Exactly as you have described ! Length of a Parcel tying Medium?

If you are doing lots of Urban riding / commuting it will wear out faster with all the start and stops, against doing long runs in the country side

If you have doubts about it Then just change it for peace of mind
"Put your Ass on a motorcycle and ride with an attitude and the "Grim Reaper" will ride in your shadow!"

Islandmagee in case you're interested?

User avatar
Rob Frankhamr
Club Member 14
Posts: 4782
Joined: Mon Jul 25, 2005 6:33 pm
Country of Residence: Scotland
Location: Kinloch Rannoch, Perthshire

Re: Friction plate wear rate

Postby Rob Frankhamr » Sun Feb 21, 2021 10:57 am

Aboslutely... If you start to run out of adjustment (i.e. can't achieve therequired lever position at the rear of the gearbox) then you can be sure that something needs attention... although it could as easily be thrust bearing, spring or pushrod issues... but otherwise, check it everytime you get the chance and ride it till it slips. They do last a very long time if they are treated well.

Rob
Robin Frankham
ImageImageImage

Frankhams retirement home for elderly Boxers.

Electrajohnt
Forum User
Posts: 30
Joined: Mon Jan 18, 2021 7:18 pm
Country of Residence: Mow Cop, England

Re: Friction plate wear rate

Postby Electrajohnt » Sun Feb 21, 2021 11:52 am

You misunderstand my obviously poorly worded question. It is not about do I or do I not change it for a new one, I know the answer to that. I was just trying to understand how long they last by receiving a collection of data. The bike I have purchased, via eBay from USofA, was stated as 36k miles. The friction plate is severely worn, a few thou left on one side and about 1/16” on the other, just got to it in time. The bike in general reflects a used 45 year old bike, so no qualms there, just scratching my head about the mileage. The engine et al appears to be undisturbed. Except the socket head cap screw holding the rotor on, the hexagon has had a mauling for some reason. The compression test on each cylinder is ok at 10 to 10.5 bar. Not bitching about what I have bought, I intended to strip it down anyway, just curious that’s all.
JohnT

User avatar
CharlieVictor
Forum User
Posts: 1979
Joined: Tue Oct 18, 2016 6:22 pm
Country of Residence: France

Re: Friction plate wear rate

Postby CharlieVictor » Sun Feb 21, 2021 12:39 pm

You misunderstand my obviously poorly worded question. It is not about do I or do I not change it for a new one, I know the answer to that. I was just trying to understand how long they last by receiving a collection of data. The bike I have purchased, via eBay from USofA, was stated as 36k miles. The friction plate is severely worn, a few thou left on one side and about 1/16” on the other, just got to it in time. The bike in general reflects a used 45 year old bike, so no qualms there, just scratching my head about the mileage. The engine et al appears to be undisturbed. Except the socket head cap screw holding the rotor on, the hexagon has had a mauling for some reason. The compression test on each cylinder is ok at 10 to 10.5 bar. Not bitching about what I have bought, I intended to strip it down anyway, just curious that’s all.
JohnT
Well, low mileage airheads are highly suspicious for starters. These bikes were made for riding, in a time when motorcycling was not a leasure hobby yet. Unless it's documented, as far as I'm concerned add 100,000 whatever to what the counter says. In which case....

Conversely, if the bike really covered 36k miles in 45 odd years, she spent more time being parked than being ridden.... which brings another whole set of possible issues, including some clutch-related...
1978 BMW R100S "Naked"
1974 Kawasaki W3 650 Replica
Image

User avatar
r75boxer
Forum User
Posts: 370
Joined: Sat Oct 01, 2005 11:56 pm
Location: Saskatoon, Canada

Re: Friction plate wear rate

Postby r75boxer » Sun Feb 21, 2021 4:03 pm

Now I'm curious too. Not about the clutch but whether it made [financial] sense to buy in NA and have the bike shipped across the pond? Are middle aged BMWs that much cheaper in the US? What about shipping? I can ship a bike across Canada or up from the US for anywhere from $500 to $750 CDN but currency conversion from US dollars to CDN is prohibitive.

Kevin
'82 R100T
'74 Moto Guzzi Eldorado
'71 R75/5

Electrajohnt
Forum User
Posts: 30
Joined: Mon Jan 18, 2021 7:18 pm
Country of Residence: Mow Cop, England

Re: Friction plate wear rate

Postby Electrajohnt » Sun Feb 21, 2021 6:19 pm

Now I'm curious too. Not about the clutch but whether it made [financial] sense to buy in NA and have the bike shipped across the pond? Are middle aged BMWs that much cheaper in the US? What about shipping? I can ship a bike across Canada or up from the US for anywhere from $500 to $750 CDN but currency conversion from US dollars to CDN is prohibitive.

Kevin
I don’t mind discussing finances. The bike was advertised by a regular USA ebayer who advertises lots of bikes and spares as free shipping. They apparently wait until they have a container load then ship to an “agent” who you collect from or he will deliver at a cost. I had to pay import duty. And another small charge, forgot what for. The bike was £2500 plus about another £300 duties as stated. Then whatever it will ultimately cost to register, I have sent that into DVLA with I think a £65 cheque.
It was a bit risky of course but as my hobby is renovating bikes to a reasonable standard, not the mind boggling standards other people seem to achieve, I am working my way through it.
The model attracted me because it’s the last of the drum braked BMW’s. Quite happy with it but just curious how many miles it will have done. Maybe as stated it’s been around the clock but general appearance doesn’t give that impression. No play or leaks in the diff., the swinging arm and drive shaft are good. Engine is quiet, front forks and wheels seem ok. Paint on the guards a bit shabby and on the swinging arm. The rear subframe was cracked just aft of the near side suspension mount. Just got some tube same size to let a short piece into the existing and made some small gussets for both sides to beef it up a bit.
JohnT

k100john
Forum User
Posts: 94
Joined: Mon Nov 23, 2009 8:58 pm
Country of Residence: UK
Location: South-east Hampshire

Re: Friction plate wear rate

Postby k100john » Sun Feb 21, 2021 7:14 pm

I had to replace the friction plate on my 60/6 back in 2005 when it started slipping. About 80,000 miles. i thought this was a bit early, but I know the previous owner had done a lot of continental touring, two up with luggage, so that might have been a factor. IMHO it would take a seriously strange riding style to wear out at 36k.
My bike now has 98k miles, looks fine for its age: no play or leaks in the diff., the swinging arm and drive shaft are good. Engine is quiet, front forks and wheels are ok. Paint on the guards is good, a bit shabby on the swinging arm.
I'm inclined to concur with CV: add 100k miles.
jp

2004 K1200GT (now sold)
1993 R80RT
1976 R60/6

User avatar
Rob Frankhamr
Club Member 14
Posts: 4782
Joined: Mon Jul 25, 2005 6:33 pm
Country of Residence: Scotland
Location: Kinloch Rannoch, Perthshire

Re: Friction plate wear rate

Postby Rob Frankhamr » Sun Feb 21, 2021 7:51 pm

I hate to say it but we're still in 'piece of string' territory. A properly adjusted and used clutch can last 100,000 miles. A badly used or adjusted clutch can be worn out in a tenth of that. In your shoes, I would be having a good look at the driven plate and the pressure plate to see if there's any sign of bluing or cracking that would signify that the clutch had been slipping badly... but then again, I'd do that anyway on any dismantled clutch.

I think that, on a 45-50 year old bike, mileage is a bit academic anyway. There's plenty of scope for parts to have worn out and been replaced several times in that period. I would just check everything, if it's serviceable then it's serviceable... if it ain't, it ain't so replace it.

Rob
Robin Frankham
ImageImageImage

Frankhams retirement home for elderly Boxers.

Electrajohnt
Forum User
Posts: 30
Joined: Mon Jan 18, 2021 7:18 pm
Country of Residence: Mow Cop, England

Re: Friction plate wear rate

Postby Electrajohnt » Sun Feb 21, 2021 8:25 pm

A question re gearbox output shaft oil seal. The spring and lip were facing outward, not into the gearbox. Is that correct?

JohnT

John Marshall
Forum User
Posts: 1212
Joined: Sat Jul 30, 2005 9:31 pm
Country of Residence: UK
Location: Exeter, the poor man's Swindon

Re: Friction plate wear rate

Postby John Marshall » Sun Feb 21, 2021 9:30 pm

Thats right.

User avatar
Rob Frankhamr
Club Member 14
Posts: 4782
Joined: Mon Jul 25, 2005 6:33 pm
Country of Residence: Scotland
Location: Kinloch Rannoch, Perthshire

Re: Friction plate wear rate

Postby Rob Frankhamr » Mon Feb 22, 2021 10:57 am

A question re gearbox output shaft oil seal. The spring and lip were facing outward, not into the gearbox. Is that correct?

JohnT


Yes, absolutely right. Machines with paralever rear suspension (GS and R models) have the seal the other way round but all other models have it with the lip outwards.

Rob
Robin Frankham
ImageImageImage

Frankhams retirement home for elderly Boxers.

Electrajohnt
Forum User
Posts: 30
Joined: Mon Jan 18, 2021 7:18 pm
Country of Residence: Mow Cop, England

Re: Friction plate wear rate

Postby Electrajohnt » Mon Feb 22, 2021 11:11 pm

Op here.
Washed every thing off in the clutch and read Snowbums article. Overall friction plate thickness is 4mm thickness. Each side of friction material measured at the inside diameter is 1,45mm and 1.38mm.
The rest of the clutch seems ok, the plain plates have a very small amount of rescession. I think I will get away with a new friction plate.
Do I need to replace the flywheel bolts, seems to be some conflicting view on that. I believe the main set pins (cap screws - M8 x 0.75 pitch) holding the clutch together need replacing.

One thing concerning me, I did not match the orientation of all the rotating parts on disassembly. I marked the flywheel orientation on the five pins so tdc matched the flywheel. Any thoughts on real potential for out of balance. Maybe if I clock the rotating parts for concentricity I will be half way to a balanced clutch.

JohnT

User avatar
Rob Frankhamr
Club Member 14
Posts: 4782
Joined: Mon Jul 25, 2005 6:33 pm
Country of Residence: Scotland
Location: Kinloch Rannoch, Perthshire

Re: Friction plate wear rate

Postby Rob Frankhamr » Tue Feb 23, 2021 10:55 am

With an unknown bike, it's Hobsons choice anyway... you have no idea whether a previous PO has reassembled the parts with some sort of balance in mind or not and you have no experience of the bike running to take a view on whether there is any impalance to speak of.

The good side is that it's very seldom a problem on airheads. The factory did mark parts where there was an acceptable imbalance but most parts were unmarked and could be assembled in any alignment. I wouldn't worry about the concenticity of the parts... if they are visibly off centre then they are either incorrectly assembled (and it's difficult to see how they can be incorrectly assembled) or they are beyond reuse and should be junked. If the friction plate is fitted off centre, then you won't be able to fit the gearbox. If you can fit the gearbox then any residual off centre will disappear the first time the clutch is pulled.

The other point to look at with ther clutch is the strngth of the diaphragm spring. This can be assessed by placing it on a flat circuit and measuring the height of the spring fingers from the surface. I doubt you'll have any issues with a R60 engine but on a R100 engine, a weak spring is a common cause of slipping clutches.

In essence, I think that you are unlikely to have issues with the clutch any time soon, just make sure you do the adjustment 'by the book' otherwise you'll end up with your left hand bigger than the right one. Early airheads don't have a light clutch at the best of times and badly adjusted, they can be a real pig.

Rob
Robin Frankham
ImageImageImage

Frankhams retirement home for elderly Boxers.

Mjolinor
Forum User
Posts: 3136
Joined: Tue Jun 12, 2018 9:38 pm
Country of Residence: United Kingdom
Location: Burnley

Re: Friction plate wear rate

Postby Mjolinor » Tue Feb 23, 2021 11:16 am


In essence, I think that you are unlikely to have issues with the clutch any time soon, just make sure you do the adjustment 'by the book' otherwise you'll end up with your left hand bigger than the right one. Early airheads don't have a light clutch at the best of times and badly adjusted, they can be a real pig.

Rob
I reckon it's deliberate to match the "not so light" throttle they have.

Should one not expect it to be such, it is after all a tank with two wheels instead of tracks. :)

User avatar
Rob Frankhamr
Club Member 14
Posts: 4782
Joined: Mon Jul 25, 2005 6:33 pm
Country of Residence: Scotland
Location: Kinloch Rannoch, Perthshire

Re: Friction plate wear rate

Postby Rob Frankhamr » Tue Feb 23, 2021 1:33 pm


In essence, I think that you are unlikely to have issues with the clutch any time soon, just make sure you do the adjustment 'by the book' otherwise you'll end up with your left hand bigger than the right one. Early airheads don't have a light clutch at the best of times and badly adjusted, they can be a real pig.

Rob
I reckon it's deliberate to match the "not so light" throttle they have.

Should one not expect it to be such, it is after all a tank with two wheels instead of tracks. :)


Now, Mjolinor -- you are accused of heresy on three counts -- heresy by thought, heresy by word, heresy by deed, and heresy by action -- *four* counts. Do you confess?

Beware the cushions!!!

Rob
Robin Frankham
ImageImageImage

Frankhams retirement home for elderly Boxers.

Mjolinor
Forum User
Posts: 3136
Joined: Tue Jun 12, 2018 9:38 pm
Country of Residence: United Kingdom
Location: Burnley

Re: Friction plate wear rate

Postby Mjolinor » Tue Feb 23, 2021 1:51 pm

I deny all charges.

Innocent until proven guilty. Please present your evidence.

Ha, you have none. I speak only the truth.

User avatar
Tincan3
Forum User
Posts: 304
Joined: Fri Jun 11, 2010 10:37 pm
Country of Residence: Scotland
Location: Isle of Luing
Contact:

Re: Friction plate wear rate

Postby Tincan3 » Tue Feb 23, 2021 2:51 pm

Hi JohnT,
For info, in relation to your initial question. My bike had 22,000 miles on it when I acquired it in 2006 (a 1975 R75/6).
It had always had a sidecar attached and the PO was an old man who only used it about one day a year (yes, really!) for the Jumbo charity rally. A few thousand miles later I spent two weeks in the Alps with quite a bit on high tracks. Since the bike was still on its original, solo gearing that meant a lot of clutch slipping (+ sidecar, remember) to make some of the ascents. Soon after returning to the UK the clutch started to slip of its own accord and I had to replace. I am sure this would have been before 35,000 miles. The, presumably, original clutch plate was really quite thin by the time I got around to replacing it. I think it was around 2.5 or 3 mm.
The replacement was written up under "which clutch plate?" for the forum at: viewtopic.php?f=15&t=22192
Enjoy!
The bike is now around 60,000 miles and clutch OK.


Return to “Airhead Q&A's”

Who is online

Users browsing this forum: No registered users and 36 guests